Vehicle alarm systems are popular and exist in a wide variety of types. One of the important characteristics of an alarm system is the way in which it is operated.
A popular way of operating a vehicle alarm system is by using a key switch which is installed on the body of the car and is operated by the driver before leaving the vehicle and upon returning to it. This type of alarm avoids the need for an alarm unit with a delay circuit because it is armed and disarmed from outside the vehicle. Another manner of alarm operation is by way of a hidden switch inside the car. The advantage of this type of alarm is easy operation. However, it requires an alarm unit with delay circuits. Another type of alarm is operated by the ignition switch of the car. In this system, the alarm unit is armed upon turning the ignition switch off (or after removing the key from the ignition switch). The disadvantage of this system is that it requires that the key be inserted into the ignition switch every time the vehicle is entered to prevent sounding of the alarm.